Process of and apparatus for impregnating webs



G. KNAPP "Jan. 16, 1945.

PROCESS OF AND APPARATUS FOR IMPREGNATING WEBS Filed June 18, 1940 R m Nm [vs/ 9 BY algal 4 in -J ATTORNEY expansion of the air'and morePatented Jan. 16, 1945 PROCESS OF AND APPARATUS FOR DIPBEG- NATING WEBSGeorge Knapp, Clayton, Mo.,

Teed Products Corporation, New

assignor to Certain- York, N. Y'., a I

corporation of Maryland Application June 18, 1940, Serial No. 341,110

12. Claims.

Thisinvention relates-to the impregnation of a web of felted fibres andmore especially to the methods of and apparatus for impregnating such afelted web with a waterproof or water-resistant saturant. The inventionparticularly relates to the impregnating or saturating of a sheet ofroofing felt with a bituminous saturant, such as asphalt, for theproduction of composition roofing and shingles.

The impregnation and saturationof felted webs has been. accomplishedinvarious ways. Particularly in the production of composition roofing orso-called asphalt roofing it commonly has been the practice to pass asheet of roofing felt through a bath of asphalt saturant maintained at atemperatureto provide the necessary fluidity for the saturant to beabsorbed by the felt. Itv has been desired in such processes to securethe absorption of 'as much asphalt as is possible for the felt to takeup so that a wellsaturated or impregnated sheet of roofing felt isproduced as a base upon which a coating of adhesive, usually abituminous material such as asphalt, is applied whlch will sealthe'impregnating material into the felt. In many cases, moreover, thisapplied coating ofasphalt, usually of higher melting point than thesaturant, serves to bind to the saturated felt base sheet a surfacing ofgranular mineral material such as granular slate, sand, talc, or other pwdered minerals.

In the endeavorv to increase the amount of' saturant which will beabsorbed by the base felt it has been proposed to apply the impregnatingmaterial, such as hot asphalt saturant, to one face of the sheet inorder to expel through the other face of the sheet the air and anymoisture that may be carried by the sheet because of its porousabsorbent capacity. By thus removing the air and moisture there areavoided certain difficulties in the roofing products made from such animpregnated sheet. Among these dimculties is the formation of blisterswhen the roofing is subjected to summer heat and sun causingparticularly of the moisture and water vapor. This expansion tends toform a pocket and to push off the coating and the surfacing material.Moreover, when the felt base is not thoroughly saturated with theasphalt saturant it remains somewhat absorbent to moisture which, inaddition to causing blisters, may cause decay of the fibrous material ofthe base and early disintegration of the roofing sheet. By applying theasphalt saturant from one side of the sheet and continuing theapplication until the saturant appears at. the other face of the similarto that used in the sheet the voids in the felted structure may be-.

come completely filled up with the saturant.

Such a process is described in the patent to John E. Miller, No.1,636,750, of July 26, 1927. It is a featureof the process of thispatent, inaddition to applying the asphalt saturant at one. face of thesheet and in several successive applications as the sheet is moved overa series of loop forming rollers, that suflicient time is providedbetween the applications to permit the sheet to absorb or draw intoitself the saturating material applied by means of a spray or jet atsaid face of the'sheet. The applications are repeated in sufficientnumber to insure that the saturation appears at the opposite face of thesheet and blackens the sheet at said opposite face at.

least for the'greater portion of its area. As disclosed in said. patentthe sheet is then passed through a bath of aphalt saturating materialprior art process first described above. The sheet thus has applied toit at both faces a final application of the saturating material. Inpractice it is then passed to a set of heated rolls calleddrying-inrolls to insure that the temperature of the sheet and theimpregnating asphalt is maintained for sufflcient time to complete therequisite absorption of the asphalt saturant. The sheet is then carriedto a coating device where at both faces of the saturated sheet there lsapplied a coating of asphalt of higher melting point than the saturantto seal the saturated sheet at both faces thereof. Thereafter the sheetmay be surfaced with a granular mineral material referred toabove in theconventional manner.

The present invention has foran object the disclosed in the MillerPatent No. 1,636,750 for the purpose of securing a greater degree ofsaturation and preventing pocketing of air and moisture carried by theair which may occur in the practice of the process of said Miller PatentNo. 1,636,750. In the practical carrying out of the process 'of saidMiller Patent No. 1,636,750, because the sheet, at the face thereofwhich is opposite to that at which the asphalt is applied, may not havehad the air and moisture completely driven through said opposite facebefore the sheet passes into the bath of asphalt saturant as abovereferred to, a certain amount of air and moisture may become entrappedat said opposite face of the Sheet. Moreover, because the con-,

trapped beneath the saturant thus applied. The

coating in some cases may thereafter be immediately applied and may sealthe thus entrapped air in the saturated and coated web. In

other cases a looper, that is, an apparatus for looping or festooningthe length of the sheet in the air, is used between the saturating bathand the point of application of the coating of higher melting pointasphalt. In such cases, even if the entrapped air is able to escape fromthe saturant, there occurs a contraction of the saturating material byvirtue of its cooling in the IOODBI'. This contraction may cause air andmoisture to be drawn in at both faces of the saturated sheet, which alsomay be trapped by the coating thereafter applied.

In order to overcome this and other undesirable efiects experienced inthe practical carrying out of the process of saturating felted webs, andparticularly by processes similar to or in accordance with the processof the Miller Patent No. 1,636,750, the invention proposes to modify theprocess described in the Miller Patent No. 1,636,- 750. Instead ofpassing the sheet into the bath of asphalt saturant as proposed in theMiller Patent No. 1,636,750, the invention proposes to apply to thatface of the sheet at which the saturating material has been initiallyapplied a sealing coating of higher melting point asphalt at such timeand at such a point in the travel of the sheet that the saturation andimpregnation of the sheet by the saturant and coating applied at saidface will be secured to a predetermined degree. As has been mentionedabove, in the practice of the Miller process the application of theasphalt at one face of the sheet is continued until the asphalt appearsand blackens a substantial part of the area of the opposite face of thesheet. In such practical operation of the Miller process the sheet maythus have absorbed 90% or more of the amount of saturant which it couldtake up if completely saturated at the temperature of the virtue of theheat of the asphalt saturant thus applied to this face of the sheet isdriven out through the relatively thin'layer of asphalt satsaturant.Within the scope of the invention the application of the sealing coatingat said first face of the sheet may be effected when any degree ofsaturation of the sheet has been accomplished by the saturant enteringthe sheet at said first face thereof. In practice, however, theinvention proposes to carry the saturation of the initially appliedsaturant to the degree usually accomplished in the practice of theMiller process. In some cases, however, a greater degree of saturationof the sheet approaching or substantially equal to complete saturationthereof at the temperature of the saturant maybe eflected by applicationof the saturant at the first facev of the sheet before applying thecoating to seal the saturant at said face of the sheet. In general,however, the coating is applied to the sheet before substantialcontraction of the saturant which would draw air ormoisture in the webhas occurred.

In order to effect complete saturation of the felted web, particularlyin such cases where the saturation through the first face of the sheetis not completely secured at the opposite face of the sheet, saturatingasphalt may also be applied at said opposite face in successive steps inthe manner disclosed in the Miller Patent No. 1,636,-

' 750. The residual air and moisture, if any, conurant which is taken upby the felt at this face of the sheet. Thus there may be accomplishedcomplete saturation of the sheet to the desired degree with theexclusion of air and moisture. Immediately after completing thesaturation of the sheet at said opposite face a sealing coating ofhigher melting point asphalt may be applied to said opposite face toeffect final sealing of the saturated felt sheet.

In this manner before substantial cooling of the saturated web takesplace, which would draw air and moisture into the face or faces thereofat which the saturating material is applied, the sealing coating isapplied to said face or faces of the sheet to seal said facesso as toprevent air and moisture thereafter from entering the structure of theweb. The heavier higher melting point coating material thus applied ispresent to follow the saturant into the structure of the felted web asthe saturant therein contracts. Thus there is maintained completefilling of the voids and interstices between the fibers of the feltedstructure and the complete saturation of the web carrying on its facesthe coatings referred to.

A further feature of the invention which may be utilized in some casesrelates to the means for insuring that the saturation applied at theface of the sheet penetrates through the sheet to the opposite facethereof and substantially completely impregnates the sheet at saidopposite face. While such a condition of the sheet may be accomplishedby increasing the number of applications and the quantity of the asphaltsaturant at the initial face of the sheet until the saturant appears atthe opposite face in sufiicient amount to insure that the whole of saidopposite face shall be covered and impregnated with the asphaltsaturant, according to my invention I may insure the spreading and thecomplete saturation at said opposite face by passing said sheet incontact with a spreading device which will spread the excess asphaltappearing at separated places on said opposite face so as to cover thewhole surface of said opposite face.

A further feature of the invention relates to subjecting the sheet to aslight squeezing action when the asphalt applied at the first face ofthe sheet has appeared at the opposite face thereof to the desireddegree. While in the prior art sheets, to which at a face thereofasphalt has been applied, have been subjected to a squeezing action tolimit the amount of asphalt carried upon or in the sheet it has notheretofore been contemplated that the asphalt saturant which has beenapplied at one face of the sheet and carried therethrough by thecapillary action of the fibrous structure of the sheet so as to appearat the opposite face thereof may be distributed in the fibrous structureat said opposite face and spread upon said opposite face by utilizing aslight squeezing action. According to the invention the slight squeezingaction to which the sheet is subjected causes the asphalt carried by thefibrous structure of the sheet to a slight extent to be squeezed outupon the opposite not yet completely saturated face of the sheet. Thusan excess of saturant temporarily appears on said opposite face of thesheet and while so appearing may be spread thereover so as to eifectcomplete and uniformly distributed saturation of the structure at thisopposite face.

The spreading device above referred to may spotter I t over the coatingor printing rolls which are used for printing the coating also embodythe device for effecting this squeezing action. Particularly whenaccording to the inventionthe asphalt saturant carried by the fibrousstructure of the sheet has been sealed in by the sealing coating at thefirst .face of the sheet. under the squeezing action return of thisasphalt saturant to the first face of the sheet is prevented and thewhole of the squeezing action is eifective to squeeze asphalt out uponthe opposite face of the sheet. Upon release of the sheet from thesqueezing action some of the asphalt saturant which has ben squeezed outupon said opposite face may return to the inner fibrous structure of thesheet but such excess as has been carried by the sheet at said oppositeface has become spread and uniformly distributed at said opposite face.7

' Immediately after completion of the spreading of this excess asphaltwhich has passed com-' pletely through the sheet and the completion ofthe saturation at said opposite face I may apply the second coatingabove referred to so as to seal the saturant in. the sheet at saidopposite face. In such case the use of the second application of asphaltsaturant according to the Miller process as above referred to becomesunnecessary. Within the scope of the invention the applications of thehigher melting point asphalt as coatings on the two faces of the sheetmay be made with only a short time interval therebetween, particularlywhen with the cooperation of a spreading device above described, orother means, the method of initial saturation from one face of the sheetonly becomes effective to fully saturate the sheet and make it ready toreceive the applications of the higher melting point coating asphalt.

In order, however, to securea better control of the thickness of thecoatings on the two faces of the sheet, preferably the coating appliedto the second face of the sheet is applied at a point somewhat removedfrom that at which the coating is applied to the first face of thesheet. By thus spacing lengthwise of the movement of the sheet thepoints of application of the coating as.- phalts, a film or layer ofcoating of definite thickness may be secured upon the face at which theinitial saturation is applied to the sheet. This layer or film ofcoating asphalt may be printed on from a roll on which the coating iscontrolled to a definite thickness. This control may be -ac complishedby any-oi the conventional methods,

such as doctor blades acting against the printing roll. The film thusapplied to the sheet may be somewhat in excess of that required uponsaid face of the sheet. By passing the coated face of the sheet againstor over a scraper positioned so that the sheet will bear against theedge of the scraper with substantially uniform pressure the coatingremaining on the sheet may be kept ofuniform thickness regardless ofvariations in the surface contour of the sheet lengthwise thereof.Application of the coating on the opposite face maybe similarlyeffected, or in some cases the coating applied at this opposite face ofthe sheet may be gauged so as to secure a uniform thickness of thefinished coated sheet.

By the above methods of saturating and coating a felted web, such as aroofing felt for production of asphalt roofing, the usual ,dip tank orcoating pan containing a bath of high melting point asphalt commonlyused is eliminated,.with the resultthat the tension necessary todraw thesheet through the bath is eliminated. No great amount of tension isnecessary to draw the sheet mineral materials on the sheet. il'special--ly with coatings which are filled with comminuted and which, therefore,are heavy and viscous, this reduction in the amount of tension isappreciable. In addition it is necessary to handle less coating when thecoating is applied with the printing roll than when coating is appliedto both faces of the sheet by passing the sheet through a bath ofcoating in the coating pan. These conditions effect savings byeliminating breaks and consequent waste, and the loss of time andexpense caused by such breaks. An improved saturated and coated sheet isobtained. one which carries a greater amount of saturation and a moreuniformly controlled coating. Moreover, a better bond between thecoating and saturated sheet is effected by virtue of applying thecoating to the saturated sheet substantially immediately upon completingthe saturation of the sheet at the respective faces thereof..

The invention will be further understood from the description of thedrawing to follow, in which the single figure shows adiagrammaticelevation of the apparatus used to carry out the processofthe invention.

At the left hand portion of the'figure is shown a saturating apparatussimilar to that disclosed in the Miller Patent No. 1,636,750. Inconnection with such a saturator commonly the sheet I is delivered inthe direction of the arrow to the roll 3 from the dry felt looper orother container for a length or roll of dry, unsaturated felt. From theroll 3 the dry felt I passes downwardly to and around the roll 5 adistance which may be 8 to 12 feet. In this downward moi gement.preferably adjacent to lower roll 5, asphalt heated to a'temperature,which may be between 350 F. and 450 F. to secure the necessary fluidityfor saturation, is delivered in the form of a jet or spray from the pipe8. This temperature may vary depending upon the type and composition ofthe felt to 'be saturated and the quality of the asphalt used. In thepassage of the sheet I upwardly from the roll 5 to the roll 1 and fromroll I downwardly toward roll'9 time is available for the saturantapplied through the pipe 6 to be absorbed by the felt sheet I. At 8 isshown a scraper bearing against the face of the sheet at.

which the asphalt saturant is applied to scrape another Jet pipe i0acting similarly to the previous scraper and jet pipe. During furtherpassage of the sheet I over rolls l5, l1, I9, 2|, 23 and 25 additionalscrapers 8 and jets l0 act respectively to remove any congealed surplusasphalt and for the further application of the saturant. The number ofrolls 3 to 25 may vary to secure the passage of the saturant through thesheet to the face thereof-which is opposite that against which the Jetsof asphalt are directed. In the particular embodiment illustrated in thefigure the number of flights or stretches of the sheet in assing overthe rolls 3 to 25 may be taken to represent those necessary to effectabout 90% of complete saturation of the sheet. withthe asphalt appearingupon the opposite face of the sheet. This selection of the number ofapplications of asphalt by mean of jets I and It may be determined forpractical reasons of space, differences in the weight and absorptivecapacities of the felt being treated, variations in the quality of theasphalt, and other considerations.

In the passage of the sheet upwardly from the roll ii the scraper I2 isarranged adjacent the face of thesheet to which the asphalt has beendirected to remove therefrom that excess of the asphalt applied by thesprays II which would interfere with the application of the coatingabout to be applied. This scraper I2 is thus arranged adjacent the roll26 so that the asphalt which must be removed is so removed before it hashad the opportunity to chill. The sheet which has thus had the excessasphalt removed therefrom is then passed upwardly to the set of rolls 2awhich may be heated by suitable means to maintain the asphalt at propertemperature and prevent undue cooling of the asphalt while-at the sametime the sheet has time to absorb the asphalt which has been applied toit at one face thereof during its passage from the roll 26 'to the roll21. This roll 21 forms part of the coating apparatus.

Saturated sheet I moving in the direction of the arrow passes around theroll 21. In contact with the opposite side of the sheet and with itsperiphery moving with the sheet is arranged the roll II dipping in theasphalt 30 carried ,in the coating pan. The roll '20 -is driven bysuitable means not shown, and carries asphalt from the bath 30upwardlytoward the sheet I passing around the roll 21. A doctor blade I:is arranged in relation to the roll a to determine the thickness of thecoating carried by the roll II for application upon the face of thesaturated asphalt sheet I. It will be noted that this coating which, asin the normal roofing practice, is of higher melting point than thesaturant, is applied to that face of the sheet at which the saturant hasbeen directed to the sheet during the saturation thereof.

Also arranged adjacent to the roll 21 and so that the coated face of thesheet passesbetween the roll I1 and the roll 8! is a scraper a. Thisquent treatment.

chine and, as well, when the finished product is around handled.

From the roll 38 the sheet I roll 81 and around rolls IO, 4|, a; ll, 41.,II,

I} and II arranged similarly tothe saturator of spray 40. The stretchesof the sheet I between the rolls 4:, u, 41, n, II, I: and II provide forthe absorption of the asphalt in the manner sim. ilar to that of theMiller Patent No. 1,686,750.

It will be noted that the first application of the saturant by means ofthe sprays I and III was sealed into the sheet I when the asphaltapplied at this face of the sheet substantially fully impregnated thesheet at said face and when the excess had been removed from said face.After the application of the higher melting point coating III theentrance of air or moisture into the sheet through said face thereof isprevented. The saturation of the sheet at the other face thereof then iscompleted by application of asphalt through the spray pipes 40. Theasphalt delivered through the pipes 40 is at a temperature such as willsecure the necessary fluidity for absorption of the asphalt into thesheet through this opposite face'thereof. Thereafter the sheet should besealed at this opposite face in a manner similar to that carried out bythe printing roll 2|. For this purpose the sheet I passes from the roll55, over the break roll '18 to secure proper alignment of the sheet,andihto the device for subse- In the particular embodiment illustratedin the figure roll I1 is arranged at the upper face of the sheet I, thatis, at that face upon which the second application of asphalt has Justbeen made.

The weight of the sheet is carried by the poll ll which conveniently maydip into the pan I! carrying a quantity of talc or mica III to preventscraper is arranged in such relation to the sheet that the sheet bearsagainst the ed e thereof with a substantially uniform pressure. As thethickness of the felted' sheet or web may vary and, therefore. the facesurface thereof may be of irregular contour rather than a plane surface.in order to secure uniform thicknessof coating upon this face of thesheet the scraper under the substantially uniform pressure of the sheetthereagainst acts to scrape off the excess coating but to leave uponthis .face of. the sheet a coating of substantially uniform thicknessconforming to the contour of the face of the base sheet, that'is, to theelevations and depressions in the surface of the sheet. v

The sheet thus coated with a higher melting point asphalt 3| containedin the coating pan Ii passes over the roll II which at its lower porti ndips into a massof comminuted material 80 such as talc contained in thereceptacle ll. There is thus applicd'to the coating 80 upon the sheeta'mineral surfacing which will prevent the coating sticking'to therollaincontact with which thesheetsubsequentlypasaesintheroofingm bbeforereceiving the sealing coating to be applied 7 sticking of the roll II tothe bottom face of the sheet I. The roll I! thus contacting the upperface of the sheet serves to spread over this face any asphalt appliedthrough the sprays II which may not yet be absorbed by the felt and toinsure thatthe-sheet at this face thereof shall be substantiallyuniformly and completely saturated to this face of the sheet. The rollI! preferably is a rubber roll or composition roll which would have thenecessary surface characteristics ef-' fectively to spread the asphaltupon the face of thesheet with which it is in contact.

From the rolls l1 and II the sheet passes beneath'a pipe or pipes II fordelivery of asphalt of high melting point to the upper face of the sheetI tocoat and seal the sheet at this face.v

The roll 01 serves to spread the coating asphalt over the face of thesheet. the roll 0,. between which and the roll I! sheetl passes, servingtomaintainthesurfaceofthesheet I incontact with the roll I'I. Thusfl:eoating'is applied so as to secure a uniform thickness of the finishedcoated sheet. ,Thereafi'er from a suitable hopper II having feed roll I!slate or other granular surfacing material-may 'bedeli'vered to .thesheet for surfacing said coating upon the In some cases the secondapplication of asphalt saturant through the pipes 40 may be dispensedsaturated through to and upon delivered to the and applying at saidopposite face of the web a sealing coating to prevent absorption of airand moisture at said opposite face of said web.

3. Process of impregnating an absorbent web. which comprises applyingthe impregnating material at one face of the web until the web issubstantially completely impregnated through to and at the opposite faceof the web, applying at said first face of the web before substantialcontrac tion of said impregnating material in said web takes place asealing coating to prevent absorp-.

tamed. Immediately upon thus securing the sub stantially completesaturation of the sheet sealing of the opposite face thereof by theapplication of coating should be effected in order to prevent drawing inof air and moisture by contraction of the saturating asphalt carried bythe as to drive from the other face of the web air and sheet. This maybe accomplished by means of print roll 80 shown adjacent the roll 31supplied from a fountain 82 containing a supply 83 of high melting pointasphalt. In order to surface the coating thus applied a hopper 85provided with feed roll 8'Lmay be arranged adjacent the stretch of thesheet i between the rolls 31 and 39 to apply the surfacing material 86to the coated sheet. The construction consisting of the rolls 4! to 55then may be dispensed with.

If desired, or necessary, a spreader roll 90 may be placed immediatelyafter the roll and in contact with said opposite face of the sheet forthe purpose of spreading any excess of the saturating asphalt which mayexist upon said oposite face of the sheet and to secure uniform andcomplete saturation at said face before application of the coating bythe roll 80. The sheet I may be held in contact with the roll 90 bymeans of the roll 92. It will be seen that effective seal- 40 ing ofboth faces of the sheet may be accomplished within the scope of theinvention by the methods and means which form a. part thereof, so as tosecure and maintain a complete and uniform saturation of the sheet atboth its faces.

Having thus described my invention what I now claim is:

1. Process of impregnating an absorbent web which comprises applying theimpregnating materlal at one face of the web, continuing the applicationof said impregnating material at said face of the web until the web isimpregnated through to the other face of said web, applying a sealingcoating at said face of the web .at which said impregnating material isapplied to seal said web against absorption of air and moisture at saidface thereof while leaving said other face of the web unsealed until theweb at said other face is completely impregnated, completing theimpregnation of said web, and then applying at said other face of theweb a sealing coating to prevent absorption of air and moisture at saidother face of the web.

2. Process of impregnating an absorbent web plurality of means spacedalong the length of I which comprises applying the impregnating mao5terial at one face of the web until the impregnating material appears atthe opposite face of the web over a substantial portion of the area ofsaid face, applying at said first face of the web before substantialcontraction of said im- 7 regnating material in said web takes place asealing coating to prevent absorption of air and moisture at said faceof the web, applying impregnating material at the opposite-face of saidwebto complete the impregnating of said web, 76

tion of air and moisture at said face of the web,

and applying at said opposite face of the web beforesubstantialcontraction of the impregnating material at said opposite face takesplace a sealing coating to prevent absorption of air and moisture atsaid opposite face of the web.

4. Apparatus for impregnating a web of felted structure comprising meansfor applying impregnating material at one face of said web and so anymoisture contained in said felted structure, means for applying at saidfirst face of the web a sealing coating to prevent entrance of air andmoisture at said face of the web, means for completing impregnation ofsaid web, and means for applying to said other face of said web asealing coating to prevent entrance of air and moisture at said face ofthe web.

5. Apparatus for impregnating an elongated web of felted structurecomprising means for moving the web in the direction of its length,means for applying impregnating material at one face of said web and-soas to drive from the other face of the web air and any moisturecontained in said felted structure, means for continuing theimpregnation of said web at said face until said impregnation at saidface issubstantially completed, and means for applying at said face asealing coating to prevent absorption of air and moisture at said faceof the web, means for applying impregnating material at said other faceof said web to complete the impregnation of said web, and means forapplying a sealing coating at said other face of said web to preventabsorption of air and moisture at such other face of said web.

6. In an apparatus for impregnating an elongated web of felted fibrousstructure, means for moving the web in the direction of its length, a

said moving web for flowing upon said face of the web at said spacedpoints asphalt saturant in heated condition to effect impregnation ofthe web from said face thereof through the felted structure to the otherface thereof, 'means for controlling the amount of saturant thus appliedto the web to leave said structure substantially saturated at said firstface without substantial excess of the asphalt upon said first face ofthe web, means for applying to said first face of the web beforesubstantial contraction of the satu rating. asphalt due to coolingoccurs a sealing coating of asphalt to prevent absorption of air andmoisture by the saturated web at said face thereof as said saturantcontracts, means for flowing asphalt saturant upon the opposite face ofsaid web at points spaced along the length of the moving web to completethe saturation of said web, means for controlling the amount of asphaltsaturant thus applied to complete the saturation without substantialexcess of said asphalt saturant upon said opposite face of the web, andmeans for applying a sealing coating of asphalt to said opposite face toprevent absorption at said face of air and moisture by the saturatedfelted structure.

7. Process of impregnating an absorbent web which comprises applyingimpregnating material at one face of-iithe web until-the web isimpregnated through to' the opposite face thereof over a substantialpart of the area of said opposite face, applying a sealing coating atsaid first face of the web to seal said web against absorption of airand moisture at said'face thereof while leaving said opposite face ofthe web unsealed, and squeezing said impregnated and coated web to causeimpregnating material carried thereby to complete the impregnation ofsaid web at said opposite face.

8. Apparatus for impregnating an elongated web of felted structurecomprising means for moving the web in the direction of its length,means for applying impregnating material at one face of said web and soas to drive out at the other face of the web air and any moisturecontained in said felted structure, means located along the-length ofthe web in the directionof its movement from said impregnating means andsupplied from a source separate from that of said impregnating materialfor applying at said face a sealing coating to prevent absorption of airand moisture at said face of the web, and means located at the oppositeface of the web and along the length of saidweb in the direction of itsmovement from said means for applying said sealing coating for applyingimpregnating material only to the opposite face of said web.

9. Apparatus for impregnating an elongated web of felted structurecomprising means for moving the web in the direction of its length,

means for applying impregnating'material at one face of said web and soas to drive out at the other face of the web air and any moisturecontained in said felted structure, means located along the length ofthe web in the direction of its movement from said impregnating meansfor applying at said first face a sealing coating to prevent absorptionof air and moisture at said face of the web, means located along saidweb in the direction of its movement from said means for applying saidsealing coating for applying impregnating material to the opposite faceof said web, and means for applying to said opposite face of the web asealing coating to prevent entrance of air and moisture at said face'ofthe web.

10; Process according to claim 7 which comprises applying to.saidopposite face ofthe web a sealing coating to prevent absorption of airand moisture at said opposite face of the web.

11. Apparatus for impregnating an elongated absorbent web whichcomprises means for moving said web in thedirection of its length. meansfor applying impregnating material to one face of said web and so as todrive out at the other face of the web air and any moisture contained insaid absorbent web, means located along the length of the web in thedirection of its movement from said impregnating means for applying tosaid first face a sealing coating to prevent entrance of air andmoisture at said face of the web, means located at the opposite face ofthe web and along the length of said web in the direction of itsmovement from said means for applying said sealing coating for applyingimpregnating materialonly to said opposite face of said web, and meanslocated between said two last named means for squeezing said web tocause impregnating material carried thereby to appear upon said oppositeface of said web.

12. Apparatus for impregnating an elongated absorbent web whichcomprises means for moving said web in the direction of its length,means for applying impregnating material to one face of said web and soas to drive out at the other face of the web air and any moisturecontained in said absorbent web, means locatedvat the opposite face oftheweb and along the length of the web in the direction of its movementfrom said means for applying impregnating material at said first facefor applying impregnating material only to said opposite face, and meanslocated between said last two means for squeezing said web to causeimpregnating material carried thereby to-appear upon said opposite faceof said web.

\ GEORGE KNAPP.

